Section 2.2.2.3 in WD-12 currently contains the following text:
"A server MAY delete a retained message if it receives a message with a zero-length payload and the Retain flag set on the same topic.
A PUBLISH Packet with a retain flag to set to 1 and a payload containing zero bytes will be processed as normal by the server and sent to clients with a subscription matching the topic name. Additionally, any existing retained publication with the same topic name will be removed and any future subscribers for the topic will not receive a retained publication. As normal means that the retained bit is not set in the message received by existing clients."
The second of these paragraphs says that the retained publication will be removed, while the first says MAY.
Actually, I just want to ensure that we remove the inconsistency, but I have a preference for the second paragraph.